3D Printing post processes – Part 3: Gluing, bonding and combining parts

Urbee Schematics
Urbee Shell
Urbee & jimkor

Designers are often limited by the 3D printer’s build capacity. How about printing in parts to be joined together?

Urbee
The Urbee concept car was 3D printed from The Fortus Production Series.Top, from left: The design was broken into 9 parts to fit into the tray size; the part in its raw printed form; Jim Kor with the Urbee prototype and FDM full-scale, functional body panels bonded.

Quick contact adhesive for Polyjet and FDM

One of the most common fix to join parts, be it separate individual pieces or a torn edge, is to glue them. Using the most common of quick contact adhesive, affectionately known as super-glue (Cyanoacrylate adhesives), printed parts can be pieced together with ease.

Super glue contains methyl 2-cyanoacrylate, which can be considered to be handled with mild toxicity. However, it does not corrode or damage Polyjet photopolymers or FDM thermoplastics. Therefore, handle glue with minimum skin contact, and use sparingly on parts to prevent a bulge of dried adhesive forming on your seams.

TIP: try light sanding to finish off the seam area such that the glued area is not so prominent. Takes some practice to perfect the technique, but definitely worth the effort! We recommend Krazy Glue for its strength and quick dry.

Epoxy gluing for Polyjet and FDM

For the more experienced users, epoxy gluing offers a higher level of bonding. Epoxy is a two part adhesive with different range such as flexible to rigid, slow to fast curing, opaque to clear color and water-proof to water resistant, all for different applications. Epoxy adhesive can be used on both Polyjet and FDM parts.

Epoxy resins (polyepoxides) are reactive polymers that contain epoxide. They need to be cured by co-reactants (hardeners) through catalytic homopolymerisation to form a thermoset polymer. Cured epoxy resins are usually categorized with strong mechanical properties and high temperature and chemical resistance. For recommendation of epoxy adhesives, visit Henkel for the Hysol series.

TIP: Usage of water proof epoxy have been known to keep FDM parts water-tight by coating all exposed surfaces. Flexible property epoxy works well in the application to glue Polyjet Tango materials. A clear color epoxy was applied to the translucent ABSi material available on the Fortus systems; it resulted in a water-proof and increased clarity of the printed part. We recommend sanding down to achieve rough edges before applying epoxy for increased exposed surfaces, leading to stronger bond.

Tack Welding

De-burring and filament-welding for FDM

What better way to bond parts than to use its original material?

Thermoplastics melt with heat, and when dried, they also offer a substantial amount of bonding strength. This method offers an overall consistency of the joint part’s material integrity or property.

De-burring uses a power drill gun with the FDM ABS filament attached to the bits head and pressed against the conjoining seams. The rotation of the filament melts slightly on its end due to the friction caused by the drill and the part. Use slight pressure to “gun” the filament into the seams for a stronger bond.

Another method uses spare ABS/ PLA filament, preheated by a hot air gun to be pushed into the seams between the printed parts. The technique requires steady hands and good gauge of temperature as you would not want to overheat the printed part as well. It is a stronger bond as the melted filament goes deeper into the seams.

TIP: Use filament of the same material as your printed part to achieve better consistency. Do not use too long a filament for de-burring as it would snap from the pressure (no more than 4cm with 1.75mm filaments). Straighten the filament before welding by blowing hot air and setting it on flat surface for easier time. Read more here.

Soldering for FDM

This bonding technique combines the parts together by partially melting the conjoining surfaces to attach it together. Due to the volume that would be sacrificed in order to bond together, designers usually offset an additional buffer volume of variable thickness in compensation.

Place the FDM parts fitted together and using a soldering gun, trace the joint seams to melt both parts. Apply force to push the two parts together and hold while you move the gun down the line. Remember to do the same if the other edge of the seam is exposed as well.

TIP: Sand down the conjoining welded seam to smoothen your part and minimize visibility of a bonded edge.

Sanded

For more information, please contact us.